Norwich Union and New Star raised the cost of exiting their property funds on Tuesday, the latest major institutions to take the measure to try to stop major outflows of cash.

Standard Life and Prudential have already reduced the value of several of their property fund, prompting fears that the huge influx of money from retail investors that has fuelled the property boom is now flowing the other way.

New Star’s £2bn UK Property Unit Trust and the £4.2bn Norwich Property Trust are two of the most high profile and popular property trusts with retail investors.

After suffering net outflows of investor cash, the companies have switched the value of investors’ units from the ‘bid’ to the ‘offer’ price, essentially moving instantly from a maximum to a minimum valuation.

The move is taken because funds have to liquidate assets in order to meet the demand for redemptions from investors. The extra cost of withdrawing holdings means that investors who chose not to make redemptions do not have to bear the costs of selling assets.

It serves to discourage investors from making redemptions, because their investment is worth less.

Standard Life reduced the value of five of its 14 property funds by 6.7% last Friday. Prudential reduced the value of its life and pension property funds by 6.1% on June 26. The New Star and Norwich Union alterations reflected reductions of 3.9% and 4.7% respectively.

Investment specialists M&G, owned by Prudential, dropped the value on withdrawls from its £720m offshore property fund by 2% earlier this month.