The opposition has challenged the government over Lord Sainsbury's £2.5 million donation to the Labour Party.

During business questions the Tories questioned the motive behind the latest donation by the billionaire peer.

Shadow Commons leader Eric Forth led the attack. "Is it mere coincidence that there's a reshuffle coming up? Could this be anything to do with considering his position? Does this mean the Labour Party is now the party of the rich?" he asked.

Liberal Democrat MP Paul Tyler also backed calls for a debate on party funding. He pointed out that the Conservatives had now received £15 million in "short money" from taxpayers.

"Now the Conservative Party is in the pay of the government I think it's time we had a debate about whether we are getting value for money," he quipped.

Bradshaw said the only reason the donation had been made public was because of the party funding reforms put in place by Labour.

He attacked the Tories' refusal to publish its donations list for the years it was in government.

"We still have absolutely no idea where the party opposite got its money in the 18 years it was in power," he said.