British support services company Interserve has made a cash-and-shares approach to peer Mouchel create a UK outsourcing powerhouse, trumping construction firm Costain.

Maintenance group Interserve said on Friday it had inked a "co-operation agreement" with design consultancy Mouchel and discussions over the offer were continuing.

Mouchel said on Thursday it was in advanced talks with an unnamed potential buyer, prompting a denial from Costain that it was the party involved.

Interserve is one of the UK’s foremost outsourcing and infrastructure companies, operating in the public and private sectors in the UK and internationally, offering advice, design, construction and facilities management services for society's infrastructure and providing a range of plant and equipment in specialist fields.