Senior Conservatives have written to Tory MPs to raise concerns about the government's decision to allow Huawei to play a role in the UK's 5G network.
In a letter, the group - which includes four ex-cabinet ministers - said there were alternatives to the Chinese firm.
They want "high-risk" vendors to be ruled out now, or phased out over time.
Foreign Secretary Dominic Raab said the decision followed a "rigorous" review by security experts and that Huawei's involvement would be restricted.