BT is facing yet more criticism over its investment in the Openreach subsidiary which supplies broadband network infrastructure for rival companies.
The Culture Media and Sport Committee accused BT of "significantly under investing" in Openreach, and called for the communications giant to "put its house in order".
The Committee said BT is likely to have underinvested by hundreds of millions of pounds, adding that this will have been a purposeful decision made in "favour the Group's priorities and interests".
BT's rivals have called, and still continue to call, for Openreach to be completely split away from its parent company. Communications regulator, Ofcom, assessed that possibility, but ruled that competitors should be given greater access to the Openreach network.
The Committee said it supports Ofcom's ruling, but stressed that if BT fails to "offer the reforms and investment assurances necessary to satisfy our concerns" it will urge Ofcom to force a full separation of the two companies.
Speaking to the BBC, Committee member Ian Lucas said: "There is a long queue for people who want broadband. It will be very familiar to those of us who remember the 1980s waiting for a phone line - it's a similar situation, weeks, sometimes months waiting for a fibre connection through Openreach and there is nowhere else to go."