Craig Kieswetter's career-best 153 put Somerset in a commanding position on the third day of the LV County Championship Division One fixture at sun-drenched Taunton.

The 21-year-old South African wicketkeeper, who qualifies for England next spring, produced an exhilarating display, blasting eight sixes and 14 fours in his 170-ball innings as his side ran up 557 for eight declared to lead by 213 on first innings.

Peter Trego contributed a sparkling 80 and Zander de Bruyn a more measured 71. By the close Lancashire had made 87 for two in their second innings and still trailed by 126.

A Somerset victory would greatly enhance their chances of runners-up spot in the Championship, but they still face the problem of bowling the opposition out twice on their flat Taunton pitch.

The home side began the day on 266 for three. Nineteen-year-old debutant Jos Buttler took his score from 13 to 30 before edging a forward defensive shot off Glen Chapple and offering a routine catch to wicketkeeper Luke Sutton.

Buttler's first Championship innings spanned 68 balls and included five fours. He showed good temperament and no little ability in a fourth-wicket stand of 78 with de Bruyn.

It was 350 for five when de Bruyn chased a wide ball from Kyle Hogg and presented a slip catch to VVS Laxman. His 147-ball innings had featured 10 fours, but the fireworks were about to start.

Trego joined Kieswetter in a stand of 183 which was a Somerset record for the sixth wicket against Lancashire. Both players are savage stroke-makers and soon the visiting bowlers were suffering in the warm sunshine.

Kieswetter reached his fourth Championship century of the season off 138 balls, with three sixes and 12 fours. He then cleared the ropes five more times in taking only a further 31 deliveries to move to 150.

Trego joined in the big-hitting, collecting three sixes and eight fours, in making his runs off 98 balls and looked set to follow his team-mate to three figures when carelessly sweeping Gary Keedy to Saj Mahmood at short fine leg with the total on 533.

Kieswetter's majestic knock, which will not go unnoticed by the England selectors, ended the ball after he passed 150 and his previous best score, made against Warwickshire at Taunton in April.

He tried one big shot too many and was caught by Francois du Plessis at backward point.

It has been a wonderful match for Kieswetter, who quickly added to his six first innings catches when Lancashire began their attempt to save the game.

With the score on 27, Sutton got a thin edge pushing forward to Alfonso Thomas and departed for 16.

Kieswetter was in action again to dismiss first innings centurion Paul Horton for 32 off David Stiff to make it 67 for two.