The prospect of Sainsbury's falling into the hands of private equity has worried the unions.

The T&G has approached Alistair Darling, secretary of state for trade and industry, to voice concerns on behalf of members working at Sainsbury's. "If private equity comes in it poses a significant risk to the stability of the company and therefore to our members, particularly when it comes to jobs and pensions," said a T&G spokesman.

The GMB has written to MPs to ask for support for an Early Day Motion that would end tax relief on interest payments on loans to venture capitalists.

"GMB are calling upon Gordon Brown in his next Budget to end tax relief for interest payments on loans used by venture capitalists to buy companies such as the AA, Birds Eye and Sainsbury's," said GMB officer Paul Maloney. "This transfer from taxpayers is leading to the destruction of household name companies by venture capitalists who are saddling these employers with massive debts."