Nick Bourne: "Morgan has failed"

But the amendment warned that funding for vital services could be at risk if the census showed a smaller number of people in Wales than was really the case.

It was the first time AMs have voted on the issue and Plaid Cymru hoped to send a strong message from the Assembly to the Prime Minister, Tony Blair.

The lack of a tick box indicating Welsh national identity on the Census form has for months now been arousing strong sentiments across otherwise deep political divides.

"If the people of Wales, through their elected representatives, feel angry enough about this issue then it is not too late to make the change even at this late stage," said Plaid Cymru's leader Ieuan Wyn Jones.

The Welsh Conservatives supported Plaid Cymru in the debate, arguing that the existing forms should be over-printed and the software upgraded.

Strong objections

Their leader, Nick Bourne, has said that Labour's refusal to do this was unacceptable.

He said it was a litmus test for standing up to Westminster and that First Minister Rhodri Morgan had failed to do so.

A spokesman for the Liberal Democrats said they supported the spirit of the Plaid Cymru argument but stood with the case made by Labour - that it was too late to change and that no party should condone civil disobedience.

Despite strong objections to the lack of a tick-box, everyone, Labour said, should fill in the forms when they arrive through the letterbox next April.

The tick box in Scotland was added at the request of the Scottish parliament, which has authority over the census in Scotland.

But London controls the census for Wales, and the Assembly can only ask Westminster to change the forms. It has no power to do so itself.

When told of the Assembly's vote, a Downing Street spokesman repeated the government's position that it was too late to change the forms and that they should be filled in as they are.