THE Coalition is attempting to paper over its internal differences over the sale of Cubbie Station to a Chinese-dominated company by proposing a motion in the Senate demanding Treasurer Wayne Swan fully justify the move.

After a split within the Coalition - with the opposition leadership backing the sale but Nationals Senate leader Barnaby Joyce leading dissent within his party - opposition Senate leader Eric Abetz and Senator Joyce yesterday gave notice of a motion backing foreign investment provided it was in the national interest - but posing detailed questions on Cubbie. The motion takes up some issues posed by Senator Joyce. It asks why Mr Swan did not extend the consideration of the bid by 90 days.

It says Mr Swan also should explain ''why the sale is not contrary to the national interest'' and release the advice the Foreign Investment Review Board had provided to him.

''The Treasurer has failed to explain why the potential sale to a majority foreign-owned consortium of one of Australia's most valuable irrigation properties, with a water licence equal to 6 per cent of the water use in the Northern Murray-Darling Basin, is not contrary to the national interest,'' says the motion, to be voted on today. It also calls for the government to establish a public register of all foreign acquisitions of agricultural land.

A spokesman for Mr Swan said last night: ''Mr Joyce has travelled the length of the country defying his leader and trashing the Liberals' economic credentials, so it will be humiliating if he now capitulates and acknowledges the Treasurer's decision is the correct decision.''