The plan, which makes it compulsory for fans to buy tickets for all cup games at Old Trafford, had previously been obligatory only for new season-ticket holders.

But for the first time this summer, it has been extended to the remaining 25 per cent of existing season-ticket holders who have not previously signed up.

United played 10 home cup games in the past campaign and a repeat of that would see a minimum of £390 added to the cost of the most expensive season ticket next season.

The Manchester United Supporters’ Trust have already engaged a leading legal firm to act on their behalf and are ready to take the matter to the courts.