British Prime Minister Gordon Brown Tuesday condemned a maintenance workers' strike on the London Underground (Tube) network that has caused massive disruption to commuters and tourists in the city, according to dpa. As the 72-hour strike called by the Rail, Maritime and Transport Union (RMT) began to bite Tuesday, Brown urged the union's members to return to work. He accused the 2,300 maintenance workers taking part in the action of "causing an enormous amount of trouble to the people of London and disruption to the business of this city." The walk-out began late Monday, and by Tuesday morning, only two out of the city's 12 Tube lines were operating. The result were massive queues, traffic chaos and people choosing to work from home. The RMT members are demanding guarantees for jobs and pensions after a private maintenance firm, Metronet, went into administration.