THE battle for the votes of millions of Sun readers began in earnest yesterday as Tony Blair wrote a personal dismissal of the paper's damning criticism of his Government's record.

In an extraordinary but not unprecedented intervention, the Prime Minister spent the morning of his Bank Holiday at Chequers this week penning a 975 word defence of the Government's achievements.

Mr Blair was stung into action when he read the Sun's screaming headline on Monday morning ''May Day, May Day, Blair in crisis over Rover, NHS, asylum and law and order''. According to a Downing Street spokesman ''he simply wanted to point out the bigger picture since the article in the paper was so unfair''.

Yesterday's triumphant Sun trumpeted the Prime Minister's hand written letter as evidence that they had ''rattled him'', a claim immediately dismissed by Downing Street.

A spokesman said: ''The headline over his letter wasn't fair. The Prime Minister was not rattled just because he had taken the trouble to write a sobered and a considered article. He thought it was so skewed it should be answered''.

No matter how much Downing Street wants to play down the significance of Mr Blair's hand written missive there is no denying the importance the Government places on the continuing support of The Sun's readership. Last night, a Downing Street spokesman admitted that The Sun was ''important'' but insisted the Prime Minister believed ''the whole electorate was important''.

Labour Party strategists believe the Sun's support at the General Election in 1997 was hugely significant if not quite the defining factor claimed by the Sun itself. Now with tomorrow's local government elections likely to give the Goverment a bloody nose and the General Election perhaps less than a year away, Labour's thinkers will be refining their press strategy.

Government advisers will insist the Government will be judged on its record rather than spin in the press but that will be to deny the importance they place on the media.

The Sun has shown, as yet, no sign of transferring its support to the Tories but yesterday a senior source warned that its support for Labour at the General Election was ''not quite set in concrete''. The Sun acknowledged the Government has never taken its support ''totally for granted'' but there is an obvious division of loyalties within the Sun.

While there are Sun executives who maintain Blair's Government still commands their support, another claimed that ''nothing is ruled out, there are still 12 months to go.''

A Sun source said: ''Our headlines on Monday were a wake up call to the Prime Minister to get him back on the issues which resonate with Sun readers.

''We think he has been spending too much time on issues like Section 28 and the Labour heartlands. No sooner had he pronounced on Asylum, he seemed to do a runner when liberals attacked his language.

''We shall continue to be critical when we think he's drifting from the plot''.

Another source, citing the Government's failure to deliver wholesale welfare reform, said: ''The Sun is about small Government and low taxes.

''This Government started out well with the independence of the Bank of England but the red tape is increasing and we do not like any Government intervention''.