Hedge fund Oasis Management Company has ratcheted up its attacks on The Restaurant Group, accusing it of withholding information from key shareholders ahead of next week’s annual meeting.

It comes as another shareholder, Royal London Asset Management (RLAM), makes public its support of the company’s management team.

Oasis, which owns a 12.3% stake in TRG, has written to chairman Ken Hanna expressing its “deep concern regarding the equal treatment of shareholders”.

The letter claims that ISS, the proxy shareholder advisory group, was made aware of a commitment by TRG to review the remuneration policy, whereas this had “not been (nor has it subsequently been) made public by the company”.

Oasis added: “We consider it deeply concerning that the company’s shareholders are being asked to approve the remuneration policy without (in the case of many TRG shareholders) being aware of the key fact that the company itself acknowledges that the new policy will need to be revisited post-AGM.”

Meanwhile the owner of Wagamama has won support from another of its biggest investors, with Sky News reporting RLAM, which owns just under 5% of TRG, will vote in favour of its board on all resolutions including directors’ re-election and remuneration.

Its backing adds to that of Columbia Threadneedle Investments, which holds a 19% stake and said earlier this month that it would back Ken Hanna, chairman, and Andy Hornby, chief executive.

Oasis has called for a strategic shake-up of the group, which also owns pubs and concessions businesses, and chains such as Frankie & Benny’s.

A TRG spokesman said: “As you will have seen from our recent trading update, the market’s reaction and upgrades from the analysts, we will continue to let our numbers do the talking.”

City sources said Oasis will oppose the re-election of Hanna and Hornby, the company’s pay committee chair and both its remuneration policy and remuneration report.

In a statement issued to Sky News, Richard Marwood, a senior fund manager at Royal London Asset Management, said: “We are supportive of the management.

“Some of the views out there, that there is value to be crystallised by changing the structure of the group, are not lost on the management team.

“They are not intransigent and are working hard, both operationally and strategically, to create value for shareholders.”

TRG issued a positive trading update earlier this month, and has been boosted by a research note from analysts at Shore Capital who cited its “robust performance”.

Shares in TRG were trading on Thursday at around 49.65p, giving the company a market value of roughly £370m.

It recently announced plans to close 35 underperforming sites, while others in the sector, such as Prezzo, are turning to insolvency mechanisms to enforce site closures.

Glass Lewis and ISS, the proxy advisers, have recommended that TRG shareholders vote with Oasis, while the Investment Association’s voting advisory service has backed Hanna over Hornby’s pay.