Armitstead, winner of the final edition of the Women’s World Cup, was hoping to secure her second straight victory this season, after marking her debut in the rainbow jersey with a win at last week’s Omloop Het Nieuwsblad.

The peloton remained together for much of the 121 kilometre course in Tuscany, which featured several gravel sections.

It caused Armitstead’s Boels-Dolmans team-mate Nikki Harris to launch an attack with 40 kilometres to the finish.

After establishing a 30 second advantage, the main field raised the pace in a bid to thwart Harris’ move and the Briton was eventually hauled back in.

The Rabo-Liv team then aimed to send Kasia Niewiadoma clear with 12 kilometres to race, with Armitstead and Swedish national champion Emma Johansson joining her in a three-woman breakaway.

Ahead of the final climb to the Piazza del Campo, Armitstead attacked her rivals and pulled away to claim the race victory in a time of three hours 30min 13sec.

Niewiadoma ended as the runner-up as the Polish rider finished three seconds adrift, while Johansson settled for third.

"It's amazing to win the first UCI women's WorldTour event and this race is absolutely special,” said Armitstead, who was runner-up at last year's race.

“After winning in Belgium last week, thankfully I'm not affected by the curse of the rainbow jersey.

“I managed to honour it again today.

“We've shared the work in the last 10km with my two breakaway companions and I pulled away on the climb, it worked out really well."

The Women’s WorldTour is due to continue with the one day Ronde Van Drenthe race in The Netherlands on March 12.

A total of 18 events are being held as part of the inaugural WorldTour, which includes both stage and one day races.