Labour is promising free full fibre broadband to every UK home by 2030 – if it wins the election – by bringing part of BT back into public ownership.

John McDonnell told BBC political editor Laura Kuenssberg that the roll-out would cost £20bn, and that maintenance of the network would be paid for by a tax on multinational tech companies.

The shadow chancellor said with an investment of public money on that scale "people would expect us to get something in return".

Boris Johnson has promised £5bn to bring full-fibre to every home by 2025.