Richard Desmond denied the donation was underhand
The comments by Tony Blair's official spokesman come against the background of growing disquiet within the Labour Party over the decision to accept £100,000 from publisher Richard Desmond.
He gave £100,000 to Labour after a decision not refer his purchase of the Express group to the Competition Commission. Downing Street has denied any connection between the two events.
Labour MP Alice Mahon said Mr Desmond exploited women and was the last person she wanted to see financing her party.
But the Conservatives want a full explanation as they raise questions about the timing of the gift and Mr Desmond's takeover of the Express.
'No moral judgments'
Halifax MP Ms Mahon told BBC Radio 4's Today programme: "What Richard Desmond does exploits women, and that's not what the Labour Party's about.
"We're in favour of equality, and as somebody who's been in favour of
promoting the position of women all my life, then obviously somebody like
Richard Desmond is the last person I would want to support and finance the
Labour Party."
But former Labour minister Glenda Jackson said she had always been opposed to censorship.
Ms Jackson told the Today programme: "I cannot understand why legal commercial operations, because some people don't find those activities morally acceptable, should be excluded from participating in the democratic political activities of their country."
That echoed the views of Northern Ireland Secretary Mr Reid.
He told BBC Radio 4's Broadcasting House on Sunday: "If you are asking if we are going to sit in moral judgment on those who wish to contribute to the Labour Party, then the answer to that is no."
The case is the latest in a series of donation rows to hit Labour.
'Following advice'
The Conservatives claim Mr Desmond's donation was made just before a change in the law forcing such donations to be made public.
Trade Secretary Stephen Byers told the BBC's Breakfast with Frost programme that he was acting in line with a previously announced policy on such cases when he decided not to refer Mr Desmond's bid to buy the Express group to the Competition Commission.
He said that in 2000 he had made clear that in future he would accept the advice of the director general of fair trading on whether to refer merger cases to the Competition Commission.
And the director general had said Mr Desmond's bid should not be referred to the commission.
'Hypocrisy'
But shadow Cabinet Office minister Tim Collins claimed Mr Byers could have intervened on the Express deal.
Labour spent the money on advertisements taken out in the Express titles in the run-up to last year's general election.
Conservative Party chairman David Davis said: "The prime minister has a lot of explaining to do.
"The timing of this huge donation, and its non-declaration, is extraordinarily hypocritical, in that it was designed to avoid Labour's own Electoral Commission legislation, which would have forced this into the public domain."
Mr Davis called for a full record of Labour meetings with Mr Desmond.
Any party donation made after 15 February 2001 would have to be declared to the Electoral Commission immediately.
'Sea of sleaze'
A Labour spokeswoman said the party had promoted "greater openness and transparency in party funding, after 18 years of secrecy under the Tories".
She added the donation was to appear in the party's annual report later this year.
But Liberal Democrat chairman Mark Oaten said: "Labour is in danger of drifting into a sea of sleaze.
"The government now needs urgently to look into the introduction of state funding of political parties."
A spokesman for Northern and Shell said: "The donation of the money to support the party's advertising spend was done in a fully transparent manner and will appear in Northern and Shell's annual accounts later this year."