Imagination Technologies, the British company that designs the iPhone’s graphics chips, has formally put itself up for sale amid a row with Apple.

Imagination’s shares rose by a fifth in early trading after it said it had “received interest from a number of parties for a potential acquisition of the whole group”.

Analysts said companies including Intel, Qualcomm or even Apple itself could be potential bidders.

Imagination, which is based in Hertfordshire, was thrown into turmoil in April when Apple said it planned to stop using its chip designs, which help power the iPhone, iPad and Apple Watch, by 2019.