Dazn, which is advised by Goldman Sachs, has sought long-term guarantees from BT that would mean it would cover the costs of BT Sport customers cancelling their subscriptions. BT is said to have refused such demands.

BT is seeking an exit from sports broadcasting nearly a decade after it ambushed Sky in the 2012 Premier League rights auction. At launch it made BT Sport free for broadband customers, in an effort to staunch the flow of defections to its then-bitter rival.

In recent years the pair have reached a truce that involves each providing access to their sports channels to the other. BT aims to exit the business to avoid exposure to the volatile rights market and allow it to concentrate on improving customer service in its core broadband and mobile operations.

A joint venture with Discovery would not give BT as swift and neat an exit as cash from Dazn. However, Discovery, which is in the midst of a $43bn takeover of WarnerMedia that will create the world’s second-largest media company after Disney, may be viewed as the more attractive partner in other ways.

Change of control clauses in BT’s arrangements with Sky give Britain’s biggest pay-TV provider sway over the discussions. Although it is not seen as a barrier to a deal with Dazn, it views the streaming upstart with suspicion after a row over football rights in Italy.

The pandemic has also led to conflicts between Dazn and sports rights holders as it sought to trim costs. It made a loss of $1.4bn the year before coronavirus devastated live sport. 

Dazn, which has UK rights to boxing matches, is seeking to acquire BT Sport as it targets a stock market float next year. Sir Leonard, who made his fortune in natural resources in the former Soviet bloc, has ploughed billions of dollars into the venture and has been seeking to share the burden since before the pandemic.

Kevin Mayer, a former senior Disney executive, has been appointed chairman of Dazn as part of preparations for a listing. He is also an adviser to Discovery, however, which has raised concerns over a potential conflict of interest in relation to BT Sport. Sources close to Mr Mayer said all his interests had been openly declared and that any potential issue had been managed.

All parties declined to comment.