'I follow the law - I don't make the law,' said Paul, who has bankrolled Labour for more than 20 years but has never disclosed how much he donated to the party.

British newspapers reported Sunday that the new law would only be enacted after the next general election because ministers claim it is 'too complex' to make immediate changes.

The decision angered MPs who have argued for change.

Lord Dale Campbell-Savours, a campaigning Labour member of the upper house of parliament, accused the government of 'wriggling out' of its commitment.

'This is not in the spirit of the undertakings given to parliament. It seems that the law has somehow been circumvented.'

Lord Matthew Oakeshott, the Liberal Democrat treasury spokesman, said he suspected Labour was concerned that the party cannot fight the cash-rich Tories in a climate of recession.

The Ministry of Justice said: 'We do not believe at present that it will be practicable, given the complexity of the provision, to commence before summer 2010, but we will keep that under review.'

A spokesman for the Electoral Commission said it was up to ministers when the new measure would be enforced, adding: 'In the meantime, the rules will stay as before and someone who is non-domiciled can still donate.'