Grafton Group has increased its stake in the builders and DIY merchants, Heiton Holdings, to 13.89 per cent from 12.14 per cent.

Rock Brook Holdings, a wholly-owned subsidiary of Grafton, wrote to Heiton last week to inform the company that it now owned 6,557,926 ordinary shares in the company.

A Grafton spokeswoman refused to comment on its stake-building in Heiton except to repeat that it was for investment purposes. But there is a widespread belief in the market that the company may be gearing up for a takeover bid for its small rival.

Meanwhile, Friends First has also increased its shareholding in Heiton and now has an interest in five per cent of the share capital of the company.