A Labour government will introduce a cap on credit card debt so no one can pay more in interest than what they originally borrowed, the shadow chancellor has announced.

John McDonnell told delegates at his party's conference in Brighton on Monday that around three million people in the UK have repaid more in interest to credit card companies than what they originally borrowed.

The shadow chancellor also used his speech to reiterate his party's pledge to extend the proposed HS2 railway line to Scotland.

During his address to the conference, McDonnell accused credit card companies of profiteering from "people's financial difficulties".

Similar interest capping measures were introduced in recent years by the Conservative government against pay day loan lenders.

"I'm calling upon the government to act now and apply the same rules on payday loans to credit card debt," said McDonnell.

He added: "If the Tories refuse to act, I can announce today that the next Labour government will amend the law."

The shadow chancellor also vowed to take private finance initiative (PFI) contracts back into public hands, a move that would cost billions of pounds.

The contracts were used by previous governments, including Labour, to receive capital from private companies to build hospitals, schools and other infrastructure projects.

PFI deals have left the public sector owing a significant amount of debt to the firms.