SNP leaders yesterday claimed to have fresh evidence of a pro-Union understanding developing between Labour and the right, despite Scottish Secretary Donald Dewar's assertion that he would never do a deal with the Tories.

They cited a meeting last week between the Prime Minister and Mr Andrew Neil, Scotsman editor in chief, at which the creation of a new right of centre think tank was discussed. Mr Neil is on the board of management and the Barclay brothers, owners of the Scotsman, have made a substantial donation.

The creation of the Scottish Policy Institute has been welcomed by the Scottish Tories, although Mr Neil has insisted that it has no ties with any political party.

SNP leader Alex Salmond said: ''The remarkable thing is that the Prime Minister himself is apparently implicated in this embryo Tory/Labour alliance in Scotland and was hearing about the new think tank from Andrew Neil on the very night Donald Dewar wasn't ruling out a Labour/Tory pact in the Scottish Parliament.''

The think tank has stated it will be ''advocating new market based policies for Scotland that will keep it prosperous and content within the United Kingdom''.

A Downing Street spokesman said: ''The Prime Minister enjoys political debate and anything that contributes to that debate is of interest to him but that's about as far as it goes.''