Brake pedal hits the floor

The brake pedal hits the floor and stops me eventual. There are no warning lights lit on the dash. When I apply the brake hard the car twists at the front end like only one caliper is working. The brake fluid is full and no sign of a obvious leak. I have been advised this may be down to the ABS pump but the people that advised me said that a lot of the dash lights came on to warn them there was an issue. If I pump the brake it gets better for a split second until I take my foot completely off the brake. When I apply pressure to the brake again the problem remains.