Dundas & Wilson energy and infrastructure head Keith Armstrong has resigned from the firm after "irregularities" were discovered in a tender pitch.

According to a report in Scotland on Sunday, Armstrong obtained confidential information about the client in question, thereby prejudicing the tender. Dundas withdrew the bid when the issue came to light and is now conducting an internal investigation, after referring the matter to the Law Society of Scotland.

Interim joint managing partner Caryn Penley said in a statement: "It was brought to the attention of the board that there were irregularities in a tender process in which the firm recently participated. As soon as we ascertained this we immediately withdrew our tender to maintain the integrity of the process."