One of the most interesting recent developments is that Brendan Nelson, former defence minister and Liberal opposition leader, is now back in Canberra as director of the Australian War Memorial after representing Australia in Brussels. His Howard government colleague, Amanda Vanstone, is also back in Australia after a stint as a diplomat in Rome and is now hosting an ABC radio current affairs program.

But many more former political leaders are becoming lobbyists. This is the case with two of the top three Howard government ministers, the former treasurer Peter Costello and the former foreign minister Alexander Downer.

This development is one of the most noticeable trends in the politics of influence over the past 30 years since the Hawke government won office in 1983. Shortly afterwards the new Labor government was faced with the Combe affair, currently revisited as part of the ABC television special Canberra Confidential. This quasi-security scare morphed into an ultimately ill-fated lobbyist registration scheme.

At that time special minister of state Mick Young commented that the lobbying profession was now an established part of the democratic political process in Canberra. Now it can be said without doubt that former political leader-lobbyists have become an established part of the political process.

This development has crept up on us slowly, achieving acceptability over the past 30 years. During the 1980s and 1990s, former politicians started to infiltrate the political advice process. But they tended to do so as individuals semi-privately trading on their individual standing as former prime ministers, such as Bob Hawke, or by joining the ''respectable'' end of the lobbying continuum as advisers to law firms or banks, like Macquarie Bank, as former NSW premiers Nick Greiner and Bob Carr did. This ''consultancy'' activity was cloaked in respectability and was not perceived as being at the hands-on dirty end of lobbying.

That pretence now seems to have ended and Downer and Costello are good federal examples. There are many others at the state level. In these two cases lobbying is just one part of their diverse portfolios, including journalism, diplomacy and Liberal Party advising. Downer was touted as a possible new state leader of the SA Liberals recently and flirted with the idea. Costello has taken advantage of the new Coalition state governments, including heading the Newman government's post-election Commission of Audit.

Downer formed the South Australian lobbying firm, Bespoke Approach, with former Labor minister Nick Bolkus and Ian Smith, husband of former Democrats leader Natasha Stott Despoja. They have set out to be deliberately multi-partisan.

Costello has effectively transplanted his former political office into the world of lobbying by teaming up in a new company, ECG Advisory Solutions, with his former staffers Jonathan Epstein and David Gazard. Gazard stood unsuccessfully for the Liberals in Eden-Monaro at the 2010 federal election. Their image is very much Liberal Party in exile.

Costello and Downer join a new world of lobbying which is now dotted with former leading politicians as well as the usual former party officials and ministerial staffers. Ex-politicians are now central rather than fringe players.

This has become clear in the background stories by my former ANU political science student Lucy Battersby, in the Fairfax Media, about the role of lobbyists and in-house government relations specialists in the politics of supermarket market share.

Woolworths and Coles are the major players. Their political aim is to prevent increased competition, aided and abetted by governments, from the likes of Aldi. The cast of former political players is remarkable, showing how much has changed in the world of lobbying.

Costello and Downer are actually on the same side in this political battle. Coles, a subsidiary of Wesfarmers, employs ECG Advisory Solutions directly to supplement its own in-house corporate affairs division, headed by long-term lobbyist Robert Hadler. Wesfarmers has its own corporate affairs division, managed by former Western Australian Labor premier Alan Carpenter. In turn, the company supplements this firepower with lobbying assistance from Downer's Bespoke Approach.

Woolworths, not to be outdone, also has its own government relations team of former Liberal and Labor advisers, under a former federal director of the Nationals, Andrew Hall. Aldi, for its part, uses one of the very biggest lobbying firms, Government Relations Australia Advisory [two dozen lobbyists and almost 50 federal clients], with former federal Labor treasurer John Dawkins as part of the team.

These big flashy teams of former senior political leaders and their staff bring process knowledge, personal contacts and political savvy.

The stakes are high and the business is big. Costello has already been targeted for alleged conflict of interest in Queensland where he both lobbies and advises government. More than pocket money is at stake. There is certainly room for conflicts of interest when politician lobbyists work both inside and outside government at the same time as has already happened with state Labor governments.

There are now so many former politicians in the influence industry that it is the ones who don't take this path who stand out as exceptions. Nelson has all the skills, experience and savvy that his former ministerial mates have, but he has chosen not to follow the money trail as a commercial lobbyist. Instead he now serves a substantial national institution; and is already making his mark, but not without controversy. In my judgment he has taken the high road as far as post-politics careers are concerned.

John Warhurst is an emeritus professor of political science at the Australian National University.

John.Warhurst@anu.edu.au