Scottish National Party MPs are warning that they may vote against the government's controversial English education reforms next week.
The education bill has proven controversial
Its MPs are seeking clarification on whether the financial implications of the bill would affect Scotland.
If the MPs decide they do, the SNP will take part in the vote - which already faces a rebellion by some Labour MPs - potentially making it even tighter.
Government sources said there may be an impact on how funding is worked out.
Labour's proposals to reform English education and establish trust schools have been hugely controversial.
The government has already made concessions in the face of a huge Labour rebellion, but next week's vote could still be tight.
While the legislation does not directly affect Scotland, the SNP believes there may be financial implications if funding of the English system changes.
That could have an impact on the Barnett formula, the method by which the Scottish block grant is calculated.
The SNP is seeking answers from Education Secretary Ruth Kelly.
Government sources pointed out that any change to the method of funding of public services in England could have an financial impact north of the border.
They said that was the reason why ministers were opposed to the idea of banning Scottish MPs from voting on English matters at Westminster.