The strategy highlights the way in which the devices are becoming the sales ploy of choice in the mature mobile telecoms sector.
Both Carphone Warehouse and Phones4U bundle laptops ready to be connected to a broadband service.
Earlier this year, meanwhile, Orange said it would launch branded laptops.
Francois Mahieu, device director at Orange UK, said that the operator was still in talks with laptop manufacturers, but added that its first broadband-connected machines would be available by September. 'We plan to evolve this offering to include fixed-line broadband and an even wider laptop range, available exclusively to the Orange brand,' he said.
Sales of laptops peak in the autumn, when students start their college and university courses, and Christmas, when the products are often bought as gifts.
3 and Orange will both be intending to capitalise on these key trading periods.
Carphone Warehouse has relied heavily on the sale of laptops this year as the company broadens its revenue base.
The laptops in 3's broadband package, which will be available by next month, will be made by HP.
If successful, it is likely that other mobile operators will follow suit.
Vodafone said it was 'considering its options' regarding branded laptops.