* Jansen will take over as CEO on Feb. 1
* Matthew Key to join board as non-executive director immediately
* BT shares have fallen over 23 pct since Patterson took top job
* Shares down over one percent in early trading (Adds background on company, incoming and outgoing CEO)
By Arathy S Nair
Oct 25 (Reuters) - BT Group Plc appointed Worldpay co-CEO Philip Jansen as its new chief executive on Thursday, ending months of speculation about who would be chosen to tackle a host of problems at Britain's biggest broadband and mobile provider.
Several media outlets had flagged Jansen as frontrunner for the job after the board and investors lost confidence in his predecessor Gavin Patterson earlier this year.
Jansen, currently co-chief executive at payment processing firm Worldpay, previously worked with Patterson at Telewest and both men also worked for consumer giant Procter & Gamble.
Jansen, 51, has been Worldpay CEO for five years and led the business through Britain's biggest financial technology IPO. He will be appointed to the board as an executive director on Jan. 1 before taking over from Patterson at the start of February.
Worldpay announced in September that Jansen would step down at the end of this year when Charles Drucker would become the company's sole CEO.
BT shares were down over one percent at 247.6 pence at 0748 GMT.
Separately, the company said former Vodafone and O2 executive Matthew Key would join the BT board as a non-executive director immediately.
Patterson ran BT for almost five years and announced some 13,000 job cuts earlier this year as the former fixed-line monopoly struggled with intense competition, an underperforming IT services unit, a huge pension deficit and criticism of its broadband plans.
A fraud left a 530-million-pound ($683 million) black hole in the company's Italian business, forcing Patterson to cut profit targets in 2017.
Announcing it would replace him in June, Chairman Jan du Plessis said the board was confident in Patterson's strategy but doubted his ability to deliver it.
Patterson won plaudits when he took BT into TV sports, going head-to-head with rival Sky in Premier League soccer rights, and back into mobile by buying market leader EE, sending shares to a 14-year high in 2015.
But a failure to hit a revenue target and a forecast of no growth in profit for the next couple of years sent BT shares to six-year lows in May and they are now down more than 24 percent since the start of Patterson's tenure.
Jansen will be paid 1.1 million pounds a year along with a cash allowance in lieu of pension of 15 percent of salary and an annual bonus of up to 240 percent of salary subject to performance.
Patterson received a total of 2.3 million pounds ($3.1 million) in the year to the end of March, according to the company's annual report -- basic pay of 997,000 pounds plus a 1.292 million pound bonus. He had missed out on a bonus in the previous year after a number of setbacks. ($1 = 0.7755 pounds) (Reporting by Arathy S Nair in Bengaluru; editing by Patrick Graham and Adrian Croft)