Manchester City have apologised after they invited volunteers to a publicity event – and told them not to wear United colours.

The Premier League champions held a media call to promote their 'Walking Football' programme at their £200million City Football Academy (CFA) on Friday and raise awareness of the game designed for over 50s.

Stars including Pablo Zabaleta and David Silva took on club legends Mike Summerbee and Peter Barnes along with a number of volunteers in a pre-arranged kickabout in front of the press and without a red shirt in sight.

Cheeky David Silva (left) flashes his skills against participants taking part in walking football initiative

Former Manchester City star Mike Summerbee (left) takes on Pablo Zabaleta at a game of walking football

And we can reveal the absence of any United colours was by design and not by accident.

A memo sent to participants ahead of the event by the club's community arm, seen by Sportsmail, lays down the sky blue law.

'Please note' it reads, 'only participants registered for our sessions will be allowed access to CFA (no spectators), the surface is the same as the tennis centre and please do not wear any MUFC kit as you won't be allowed in'.

It is understood the message was meant to be lighthearted but the tone was lost in translation.

However, the club have been moved to say sorry.

A spokesperson for City in the Community (CITC) said: 'Manchester City would like to apologise for any offence caused as a result of the letter sent to participants of our ‘Walking Football’ project.

Silva takes on the volunteers who were light-heartedly told not to wear Manchester United colours

'CITC delivers 34 different programmes to 45,000 people in Manchester every year, and our participants wear many different colours. CITC is committed to providing footballing opportunities for all regardless of which team they support.

'The letter was addressed to the regular participants of the project and was related to the one-off event involving both current and past MCFC players. It is not a policy for CITC, nor will it be repeated.'