The advice came as Lasmo's advisers lobbied the Takeover Panel over a decision to prevent it voting a 2 per cent block of shares on its own behalf.
By blocking the 2 per cent, Enterprise would need only a majority of the remaining 98 per cent of shares.
Lasmo is asking that its 2 per cent be eliminated from the vote, so that the count would still be based on 100 per cent of the total.
The three brokers rejecting the bid yesterday included UBS, owner of the fund manager PDFM, which controls 16 per cent of Lasmo and 5 per cent of Enterprise.
Although UBS's rejection gave no indication of which way PDFM would vote, the news sparked speculation that the key investor was cool on the deal.
Enterprise executives met PDFM on Monday evening, and the Lasmo team are due to meet the fund manager today.
One analyst said: 'I can't believe PDFM would make up their mind before seeing Lasmo, but everyone is trying to second-guess them.'
The other brokers coming out against the deal were Nomura and Smith New Court.
Kleinwort Benson, Hoare Govett and Yamaichi have also advised rejection.
Enterprise shares yesterday rose 8p to 408p while Lasmo were unchanged at 141p.Reuse content