A stake of almost 50%, worth more than £800m, in the holiday group Thomas Cook is set to be placed with institutional shareholders this week.

The share sale is the most dramatic money-raising move by creditor banks of the stake’s owner, Arcandor, the German conglomerate that filed for bankruptcy in June.

It should lead to 44% of Thomas Cook’s shares being placed in the market. Market sources said demand for the stock was likely to be strong and indicated that the shares would be placed at a small discount to the current price of 229Çp.

Arcandor collapsed in June after failing to win loan guarantees from the German government. One of its main assets was the 53% holding in Thomas Cook, the travel group with brands including Airtours, Club 18-30 and Neilson.

The bulk of the stake, totalling 44% of Thomas Cook shares, had been pledged to Arcandor’s three main lenders as collateral on a €1 billion (£870m) loan. The banks — Royal Bank of Scotland, Commerzbank and BayernLB — will place the shares to recoup as much of the loan as possible.

Sources insisted that while no final decision had been taken, the banks are working towards selling the shares this week, with take-up likely to be helped by the buoyant market conditions. The placing is being handled by UBS, RBS and Commerzbank.

The consortium is known to have looked also at selling the shares in a single block to a rival tour operator but that has proved difficult.

Arcandor’s remaining 9% stake in Thomas Cook is pledged to buyers of a convertible bond. It is not yet clear what will happen to those shares. As well as its stake in the travel firm, the Essen-based conglomerate owned the department store chain Karstadt and the mail-order business Primondo.

Uncertainty over the future of such a large stake has weighed heavily on Thomas Cook shares, which have underperformed the FTSE All-Share index by 2.5% over the past three months.

Sentiment has not been helped by the recession, with talk that the so-called “staycation” trend for people to holiday at home has dented business. However, Thomas Cook and its rival Tui Travel have both reported that demand has picked up in recent weeks, largely because of the disappointing summer weather in Britain.

Thomas Cook is one of the largest tour operators in Europe. It serves more than 22m customers and runs a fleet of 93 aircraft. The group, which merged with another rival, MyTravel, in 2007, is headed by Manny Fontenla-Novoa, the chief executive.

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