The vast majority of phone and broadband faults will have to be fixed within two working days under new rules expected to be introduced this summer.
The target is part of new standards set by Ofcom for Openreach, a subsidiary of BT that installs and maintains connections to BT's network on behalf of competing providers.
Openreach will have to ensure that most customers wanting a new line receive an appointment within 12 working days and it will also have to report publicly on its performance to allow Ofcom to monitor and "intervene further if required".
Ofcom said Openreach would face sanctions, which could include fines, it if fails to meet its obligations. The targets escalate over three years, reaching their full level in April 2016.
Separately, Ofcom will also review the standards of redress, which could include compensation, that landline and broadband providers offer to consumers when services go wrong.
The draft statement is part of Ofcom's Fixed Access Market Reviews, a wide-ranging set of decisions in the wholesale telecoms markets used by companies to offer telephone and broadband services to UK consumers.
Different broadband providers sell superfast services over BT's network and there are now around 2.7 million such connections in the UK.
Currently, if a consumer wishes to change superfast broadband provider, the company they are switching to must pay a £50 fee to Openreach – which is often passed on to the customer. Ofcom said it intends to cut this wholesale fee to £11, which would allow providers to offer lower retail start-up fees.
And where an existing superfast customer switches to a different supplier, the minimum length of the wholesale contract between BT and the new supplier would reduce from a year to one month, giving flexibility for telecoms providers to offer shorter retail contracts.
Ofcom's statement follows BT's announcement that it is to create 1,600 engineering jobs amid moves to improve customer service and install lines and fix faults more quickly.
BT said: "Openreach is committed to improving its customer service levels so we support the new targets outlined by Ofcom today. The creation of a further 1,600 engineering jobs over the course of this year will help us to continue to meet or exceed these standards.
"We have also stated that we will publish regular performance data on the Openreach website from this summer to increase transparency.
"Regulation needs to reflect the level of competition in the market so it's only right that Ofcom is levelling the playing field by largely removing the artificial price difference between the wholesale products consumed by the LLU (local loop unbundling) operators and those bought by other companies.
"We feel Ofcom could have gone further however by addressing this imbalance immediately rather than over a three year period."