Substantial job cuts are inevitable as the Ministry of Justice slashes its £9 billion budget by £2 billion from October, staff have been told.

Ann Beasley, the director general of finance for the Ministry, told senior staff efficiencies alone would not be enough to make the cuts that are needed.

"There will have to be less of us as we cannot streamline the organisation to work effectively and efficiently without considering staff numbers," she said.

Details of the cuts were exposed in a letter leaked to the Public and Commercial Services Union.

In the letter, Ms Beasley said the department was in negotiations with the Treasury and further details could not be revealed yet.

But she added: "Many savings will have to be made quickly within the first 12-24 months. Efficiencies alone will not be enough. It will mean we have to look at every opportunity to work differently and better. It will also mean there will have to be less of us."