The Stock Exchange is likely to seek a clarificatory statement from De La Rue to allay concerns about a false market in the company's shares.
Although De La Rue was yesterday maintaining its policy of not commenting on market rumours, it was identified as the bidder for Portals, one of its biggest suppliers.
Shares in Portals were sent soaring on Friday when it was forced to disclose that it had received a takeover approach. The share price had already moved up quite sharply as market speculators got wind of a possible deal.
De La Rue is not expected to make an offer for Portals - which would have to be pitched at more than pounds 500m - for some days. Jeremy Marshall, De La Rue's chief executive, has made it clear that he would much prefer an agreed deal to a hostile bid, particularly on such a large acquisition. It is thought that the two sides are still some way from an agreement.
Portals is a well regarded company that recently reported a 22 per cent rise in yearly profits to pounds 31m. De La Rue is more than three times as big, with a stock market value of about pounds 1.7bn. Although the group has previously given the impression that it did not want to move into paper-making, it is unusual among the main security printers in not owning its own paper manufacturing business.
Les Cullen, De La Rue's finance director, says the group has an excellent relationship with Portals.
It is not clear how Portals' water treatment and computer control businesses will fit with De La Rue, which is tightly focused on currency, security printing and payment systems.Reuse content