The prime minister has clashed with a senior MP over the delivery of Whitehall efficiency savings.

Thursday's dispute came as Gordon Brown gave evidence on a range of issues to the Commons liaison committee.

As Leigh raised the issue of avoiding government waste, Brown replied that there would be Whitehall efficiency savings over and above the £25bn as set out in Sir Peter Gershon's efficiency review.

When Leigh countered that "you haven't achieved efficiency gains", Brown immediately replied "I do not accept that – we have achieved Gershon [targets]".

Leigh moved on to questions surrounding existing PFI projects, which he feared would suffer during the current economic climate.

Brown insisted that many projects were going ahead as planned and added that the Treasury would be announcing in the next few days how it would take forward existing schemes.

Education committee chairman Barry Sheerman picked up on Leigh's theme and asked specifically if flagship PFI projects – such as the Building Schools for the Future programme – were in the trouble that witnesses to his committee had suggested they were.

The prime minister said that he had been told that no BSF schools had failed to reach financial closure. He added that half a dozen banks had stated that they were in the market to finance PFI projects.

Sheerman also questioned how the government would encourage the roll-out of apprenticeships in the public sector, with the prime minister replying that an extra 35,000 public sector apprenticeships would be funded this year.

Home affairs committee chairman Keith Vaz questioned the usefulness of the Office for National Statistics collecting data regarding the birthplace of workers in the UK who have a legal right to work here. He was also concerned that Brown's statements concerning 'British jobs, for British workers' could be used by the far-right. The prime minister told Vaz that any comment taken out of context could be misleading.

On the government's introduction of a points-based migration system, Brown said that "where people have skills we should welcome that but where there is an area where skills are not needed we should be honest and say that we do not need them".

"The points system will address that," he added.