AT least five key senators are refusing to rule out crossing the floor over the Government's planned tough new immigration laws. Prime Minister John Howard today conceded he was not sure the laws would make it through the Senate when they come up for debate on Monday and Tuesday. Three Liberal backbenchers yesterday set the stage for a revolt and crossed the floor to vote with Labor against a Bill designed to send all asylum seekers arriving in Australia by boat offshore. Petro Georgiou, Russell Broadbent and Judi Moylan were joined in spirit by fellow Liberal Bruce Baird and Nationals MP John Forrest who both abstained. But the Migration Amendment (Designated Unauthorised Arrivals) Bill passed the lower house, where the Government has a clear majority, easily.