The Daily Telegraph's stablemate, The Spectator magazine, has secured a £100 million sale to hedge fund tycoon Sir Paul Marshall. As a result, the other bidders have been given a deadline to adjust their proposals.

Telegraph's suitors have been told to submit revised offers by 27 September as Sir Paul Marshall prepares to take control of the current affairs magazine, Sky News understands.

It comes after bidders began holding talks with Telegraph bosses last week about the company's business plan.

The remaining parties are understood to include Sir Paul and National World, the London-listed media group run by newspaper veteran David Montgomery.

At least one other party whose identity has yet to be disclosed publicly is also in contention to buy the newspapers.

A separate bid orchestrated by Nadhim Zahawi, the former chancellor, is the subject of bilateral discussions with IMI, the Abu Dhabi-based venture which wanted to take a controlling stake in the British media assets before being blocked by the government.

Sky News revealed exclusively last month that Sir Paul was the frontrunner to buy The Spectator, which along with the Telegraph titles was owned by the Barclay family until their respective holding companies were forced into liquidation last year.

His deal for The Spectator, which will be implemented through Old Queen Street Ventures, will be announced this week, and potentially as early as Monday.

It will also include the art magazine Apollo.

RedBird IMI, a joint venture between IMI and the American investor RedBird, paid £600m last year to acquire a call option that was intended to convert into equity ownership.

A sale of The Spectator for £100m would leave it needing to sell the Telegraph titles for £500m to recoup that outlay in full - or more than that once RedBird IMI's fees and costs associated with the process are taken into account.

One source said the price RedBird IMI had secured for The Spectator had exceeded expectations and left it well-placed to break even on its investment.

"The original decision to pre-empt an auction has been vindicated by the level of interest since it started," the source said.

Of the unsuccessful bidders for the Telegraph, Lord Saatchi, the former advertising mogul, offered £350m, while Mediahuis, the Belgian publisher, also failed to make it through to the next round of the auction.

Lord Rothermere, the Daily Mail proprietor, pulled out of the bidding earlier in the summer amid concerns that he would be blocked on competition grounds.

Sky News recently revealed that Mr Zahawi had sounded out Boris Johnson, the former prime minister, about an executive role with The Daily Telegraph if he succeeded in buying the newspapers.

IMI is controlled by the UAE's deputy prime minister and ultimate owner of Manchester City Football Club, Sheikh Mansour bin Zayed Al Nahyan.

The Lloyds debt, which totalled more than £1.15bn, was repaid by RedBird IMI on behalf of the family.

RedBird IMI's attempt to take ownership of the Telegraph titles and The Spectator was thwarted by the last Conservative government's decision to change media law to prevent foreign states exerting influence over national newspapers.

Spokespeople for RedBird IMI and Sir Paul declined to comment.