Lord Foster is considering widening staff ownership of shares in Foster + Partners.

He is in the process of negotiating the sale of a minority stake in the firm with a shortlist of two private equity firms, one of which is 3i.

A spokesperson for the company said the plan was to offer some senior employees shares in the business as a reward for their loyalty.

The business is thought to be worth between £300m and £500m. Foster is expected to remain at the practice for up to five years even if a sale goes ahead.

At the moment Foster owns about 90% of the equity of the company. The balance is owned by the three senior partners, Spencer De Grey, David Nelson and Graham Phillips who were promoted two years ago.