An Act of Parliament to ratify a new EU treaty not only alters the external relationship between the British state and foreign states, but also the internal constitutional relationship between the British state and its citizens.

The Irish Republic has a codified constitution, which can only be amended by referendum. That is why the Irish government has been compelled to hold a referendum on each of the EU treaties.

At one time Labour politicians were in favour of referendums to settle constitutional questions, for example whether there should be devolved government in Scotland.

But their enthusiasm for letting us have our say began to wane when voters in north east England threw out Prescott's proposal for an elected regional assembly.

Nonetheless, every Labour MP was elected in 2005 on the manifesto promise of a referendum on the new EU treaty, and they must not allow themselves to be bullied into breaking their word.

Dr D R COOPER, Maidenhead, Berkshire.