A senior trade union leader is warning that he will oppose any move for Britain to join the single currency this side of a general election.

In a New Year message Bill Morris, the general secretary of the Transport and General Workers' Union, says the rules governing membership of the euro could jeopardise investment in public services.

	:	At-a-glance
Euro basics: Your need-to-know guide

Mr Morris has already sounded a note of caution about Britain joining the euro, but now he seems to be hardening his line.

In his words, joining the single currency should be a "no no" this side of a general election - even if the Treasury's five economic tests are met.

Investment

Mr Morris fears the rules governing the euro-zone could limit the amount the government spends on hospitals and schools.

He says that if a choice has to be made it should be for investment and not the euro.

Mr Morris also warns that joining the single currency might harm the economy.

Highlighting Germany's high unemployment Mr Morris says he does not want Britain's economy to go the same way.

Scepticism

The union leader is an ally of Chancellor Gordon Brown and his comments appear to reflect some of the recent scepticism coming from the Treasury.

In September Mr Morris told BBC Radio 4's Today programme: "The prime minister should rule out a euro referendum, guarantee a third term and then return to the issue."

The government has given itself until next June to rule on its five economic tests for entering the single currency.

The pro-euro lobby say that they are still confident there will be a referendum before the next general election.