The only reason Liberal candidate for Griffith Bill Glasson is not heading to Canberra is because of the unpopularity of Prime Minister Tony Abbott, a senior Labor MP says.

Labor's Terri Butler has claimed victory in former prime minister Kevin Rudd's Brisbane seat of Griffith, despite her opponent Dr Glasson refusing to concede defeat.

With about 80 per cent of the vote counted Ms Butler holds a lead of 52.33 per cent on a two party preferred basis.

Dr Glasson is waiting for postal votes before conceding, saying he expects the vote to narrow in coming days.

Labor frontbencher Brendan O'Connor said the result was a good one for the party, saying Dr Glasson was "no ordinary candidate".

"High profile, very popular, cashed up. He lost. He'd be very disappointed," Mr O'Connor told ABC Television on Sunday.

"The only reason he's not heading to Canberra is because of the unpopularity of Tony Abbott."

However, Liberal frontbencher George Brandis said it was Labor who should be disappointed by the result of Saturday's byelection, after a suffering a slight swing against them.

"In a seat that until a few months ago was the safest Labor party seat in Queensland, to just fall over the line in a by-election is a very poor result for the Labor party and for (Labor leader Bill) Shorten," he told Sky News.

Senator Brandis also expected the result to narrow with more than 10,000 postal and pre-poll votes still to be counted.

"I think it is too early to declare victory or to concede defeat although I would acknowledge that the most likely outcome from here is that the Labor party will fall over the line," he said.

AAP