BCP said that as a result it had decided not to progress a potential offer for M&B, but it "reserves the right to make a recommended offer for the company at a future date."
Six Continents, M&B's original parent company, which demerged last month, rejected a £2.8bn pound bid from BC Partners for its pubs and restaurants arm back in March.
M&B, which owns the All Bar One, Harvester and O'Neills chains, has apparently managed to rebuff BCP's attempts to look at its figures. In its statement this morning, the private equity firm said somewhat grumpily that it had "not been given the opportunity to undertake due diligence on M&B".
It added that it was "not aware of any process being organised to seek offers for the company," a comment seemingly designed to prod investors who might be hoping for a lucrative bid for M&B and who would therefore put pressure on M&B's management to co-operate more with potential bidders.