Liverpool fans group Spirit of Shankly have taken their opposition to the club's American owners George Gillett and Tom Hicks on to the streets of the city with a billboard campaign.

Several huge posters have sprung up on major routes into Liverpool with the message "Tom and George, Debt, Lies, Cowboys. Not welcome here."

It is the latest venture in the group's campaign to pressure Gillett and Hicks into ending their tumultuous reign, which has been plagued by financial constraints and a failure to start work on a promised new 60,000-capacity stadium in Stanley Park.

"We, as fans, are unhappy with Gillett and Hicks and this is part of the campaign to show they are not welcome," Spirit of Shankly spokesman Jay McKenna said. "Previously the protests were limited to match days but we are doing everything we can and decided to expand it to other areas."

McKenna, however, dismissed any possibility of his group linking up with Manchester United counterparts – who are also unhappy at the level of debt the Glazer family have brought to their club – in a joint protest at the Barclays Premier League match between the two at Old Trafford on 21 March.

"It is a complete non-starter," he added. "The idea that Liverpool and Manchester United fans will walk down the same road together is never going to happen."