The US private equity firm trying to buy Morrisons (MRW.L) should increase its offer to around 6.5 billion pounds ($9 billion) to merit engagement from the British supermarket’s board, according to a top ten shareholder in the retailer.

Morrisons – Britain’s fourth largest grocer after Tesco (TSCO.L), Sainsbury’s (SBRY.L) and Asda – this month rejected a proposed 5.52 billion pound cash offer from Clayton, Dubilier & Rice (CD&R), equivalent to 230 pence a share.

“In our view there is validity to a bid…,” said JO Hambro, which manages funds accounting for 3 per cent of Morrisons. “We believe any offer for the group approaching 270p per share merits engagement and consideration.”

Shares in Morrisons were down 0.17 per cent at 235.6 pence at 1100 GMT.

JO Hambro noted CD&R’s existing ownership of petrol forecourt group Motor Fuels Group (MFG).

It said if CD&R were to buy Morrisons, the combined group would have around 1,200 forecourt sites across the UK.

“The fuel purchasing and food retailing synergies here are clear to see. But CD&R should pay a fair price in order to access those synergies,” JO Hambro said.

It said it believed a valuation of 8 times earnings before interest, tax, depreciation and amortisation (EBITDA) “seems reasonable given the group’s qualities and the potential synergies on offer.”

Analysts expect CD&R to come back with a higher offer and believe other suitors could be flushed out, including possibly Amazon (AMZN.O), which has a partnership deal with Morrisons.

A spokesperson for CD&R declined to comment.

Last week Legal & General Investment Management (LGIM), which Refinitiv data shows as having a 1.58 per cent stake in Morrisons, said it did not expect a bid at 230 pence to succeed.

Silchester, Morrisons’ biggest shareholder with a stake of 15.2 per cent according to Refinitiv data, has declined to comment.