Britain's biggest broadband and telecoms group announced the news less than a week after a source confirmed it had also appointed boutique advisory firm Robey Warshaw to help with its largest shareholder, Patrick Drahi.

The Franco-Israeli telecoms entrepreneur surprised investors earlier this year when he announced that he controlled 12.1% of BT, making him the biggest shareholder.

BT shares hit an 18-month high in June of 207 pence, in the days after Drahi confirmed his stake purchase, but have since steadily declined to a low of 135 pence at the beginning of last week.

News of the boutique appointment and the cost savings target have sent the stock higher, before BT reports results on Thursday. The stock was up 4.7% at 145.5 pence at 11.23 GMT.

"Further to weekend press speculation, BT confirms that it has delivered on its 1 billion pound of gross annualised cost savings 18 months ahead of the March 2023 target," it said.

The Telegraph reported at the weekend that BT was now grappling with whether to announce new targets immediately or wait until after Drahi is allowed to launch a takeover in December.

($1 = 0.7324 pounds)

(Reporting by Kate Holton; editing by James Davey)