The Tube stoppages, also scheduled for 3, 8 and 16 July are expected to mean a virtual shutdown of the service and train drivers' leaders warned of more walkouts to come.
While Aslef, the drivers' union, has avoided disrupting travel during the Euro 96 football competition, the first two strikes will coincide with the fortnight of lawn tennis championships at Wimbledon in south- west London.
Drivers voted 1,060 in favour of action with only 187 against. Lew Adams, general secretary of Aslef, accused management of reneging on an agreement to cut the working week from 38.5 to 37.5 hours by trying to attach productivity strings to the deal.
Management has offered a 3.2 per cent pay increase as part of the package and calculates that the proposals could lead to drivers earning up to pounds 25,436 a year.
A spokesman for London Underground said: "Strikes will not help anyone - our customers, our staff or our business."
Talks are due to resume on Monday.
In a similar dispute the RMT transport union, with the largest membership on the Tube system, is also expected to announce a large vote in favour of 24-hour strikes on 10 July.
The first day-long postal stoppage in protest at a pay and productivity package, including teamwork, is due to begin with the last shifts tonight. A second 24-hour strike is threatened to begin at noon next Thursday.
The Royal Mail said it had been notified of a stoppage from noon on 27 June to noon the next day by up to 134,000 postal workers following a walkout planned for tomorrow.
A spokesman described the move by the Communication Workers Union as a "slap in the face" for customers. The Royal Mail said there was no reason for the union to "rob the nation" of its mail service while talks were continuing.
"This is simply midsummer madness. Royal Mail's customers will find it very odd that with a ground-breaking deal offering more money, job security into the next century and a shorter working week on the table, the union is using tactics reminiscent of the Sixties."
Talks between the union and the Royal Mail were adjourned last night without any agreement being reached.Reuse content