The Government was defeated in the Lords last night when peers voted by a majority of 52 to delay ratification of the European Union's Amsterdam Treaty until UK fishermen were ''legally protected'' against quota hopping.

Voting was 160 to 108 for a Tory amendment to the European Communities (Amendment) Bill.

It was the Government's 20th defeat in the Lords since the General Election and will bring renewed Labour pressure for Ministers to implement their plans to end hereditary peers' voting rights.

The Government seems certain to reverse the defeat when the Bill returns to the Commons.

The report stage amendment states that the measure should not come into force until Parliament had ''come to a resolution on a motion tabled by a Minister of the Crown considering the legal protection for British fishermen afforded by the Treaty of Amsterdam on the issue of quota-hopping''.

Lord Moynihan, for Tories, said the agreement reached by EU leaders at Amsterdam last October had not lived up to the Prime Minister's pledges soon after the General Election.

He claimed the Government's gear had ''shifted down from overdrive to reverse''.

However Government Whip Lord Whitty, for Foreign Office Ministers, accused the Tories of ''pre-election posturing''.

Lords Leader Lord Richard later blamed the defeat on hereditary peers' votes.