Ministers will be delighted that The TES millennium poll shows that two-thirds of parents believe teachers’ pay should be linked to their performance.

But the news will be a blow to the unions - and especially the National Union of Teachers - which have vehemently attacked “payment by results”. A recent NUT survey showed that four out of every five members opposed the reforms.

And while the other unions have taken a more conciliatory approach, the NUT has a mandate from its members to take industrial action - including a boycott of appraisals.

In the early Nineties, parental support helped teachers win key concessions over national curriculum tests. But historically teachers win few battles on their own and union leaders will be wary of taking on the Government without parents’ backing.

The poll shows a majority of parents in all reions of England and Wales are in favour of the change. But it is not all bad news for the unions.

Despite the prospect of another tough wage settlement for teachers, there is clear support among parents for higher pay. Nearly half believe teachers are under-paid while only one in 20 says they are not worth their wages. Four in 10 of those who back performance pay also believe teachers are under-paid.

Support for higher pay is greatest in London, where more than 50 per cent of parents believe that teachers get a raw deal. This figure drops to less than a third in Wales - perhaps reflecting regional differences in income.

Only half believe that it is possible for teachers’ performance to be measured. Two in five say it is impossible. including a quarter of those who back the reforms.

The reforms are least well supported in Wales where 51 per cent say teachers should be paid by performance compared with more than three quarters in London.