Tony Blair has become embroiled in yet another row over donations to the Labour Party.

This time it is after the revelation that Science Minister and former supermarket boss Lord Sainsbury will bankroll the party to the tune of £2m this year - around 10% of its total income.

On the surface there is no great surprise in the announcement. Lord Sainsbury has regularly contributed to Labour and most believe he has donated huge sums.

Until now the party has always been shy about its big givers. The minister, for example, does not appear in records as a donor last year.

But Mr Blair is committed to introducing legislation to force all political parties to reveal the names of donors and the sizes of their gifts.

The move was originally seen as a way of embarrassing the Conservative Party, which has traditionally been even more secretive than Labour.

But William Hague has now pledged to reveal his party's big backers and the new legislation looks like it may prove just as embarrassing to Labour.

Calls to quit

Lord Sainsbury is a backer of GM technology and has been embroiled in the row surrounding them.

The opposition has previously called on him to resign from the government because of what they claim was a conflict of interest. They have seized on the latest announcement to hammer home their point.

Labour sources, for their part, insist it is hugely unsurprising that one of its richest supporters should finance it to such an extent. They are even boasting about it.

And it is insisted there is no conflict of interest with his job, and that there is no way he could use his support to influence the prime minister over the GM issue, or any other.

However Lord Sainsbury's statement is being seen by critics as a pre-emptive strike to head off inevitable controversy when new Labour laws would have forced him to publish his support anyway.

And some Labour members also believe there is something uncomfortable about big businessmen bankrolling the party.

Mr Blair has previously been caught up in funding rows concerning Formula One boss Bernie Ecclestone's £1m donation at a time the government was considering a ban on tobacco advertising ban at events.

And millionaire former minister Geoffrey Robinson, who helped fund the party, was constantly facing questions over his finances.