The hosts were 37-6 chasing 78 to win, and were eight wickets down with the scores level before Dom Bess was stumped off Keshav Maharaj's bowling.

Maharaj (7-37) then had last man Jack Leach, who earlier returned career-best bowling figures, caught at deep mid-wicket to complete a thrilling climax.

It was the first Championship match to end in a tie for 15 years.

The competition's most recent tie before this one was between Warwickshire and Essex in April 2003.

At Taunton, the result appeared to end Somerset's lingering title hopes.

Leaders Surrey asked Essex to follow-on in their ongoing match at Chelmsford and they seem certain to extend an advantage over Somerset that now stands at 21 points, with both sides having three games left to play at the end of this round of fixtures.

• Relive day two's County Championship action

Meanwhile, further questions are sure to be asked of the Taunton pitch after 13 of the 22 wickets to fall on day one were taken by spin bowlers, followed by Somerset's spectacular collapse on the second afternoon.

An incredible second day's play had started with home spinner Leach taking 7-74 as Lancashire were bowled out for 170 in their second innings.

He appeared have put the hosts on the brink of victory by registering career-best match figures of 12-102, but nobody foresaw the drama that followed.

Veteran seamer Onions (3-28) dismissed Marcus Trescothick and Azhar Ali with successive balls, taking him past the milestone of 50 Championship wickets this season, and three wickets before tea for South Africa spinner Maharaj made Lancashire slight favourites.

England Test all-rounder Bess appeared to be guiding Somerset home but, with one run required for victory, failed to connect when coming down the pitch to Maharaj and was stumped by Dane Vilas.

Onions bowled a maiden over to Jamie Overton to prolong a gripping finale, before Leach picked out Tom Bailey on the boundary, giving Maharaj match figures of 11-102.

Pitch was below average - Allott

Lancashire cricket director Paul Allott (right) spoke to ECB cricket liaison officer Dean Cosker before the second day's play began at Taunton

Lancashire director of cricket Paul Allott:

"The pitch, in my view, was certainly below average and could have been rated poor on the ECB scale. It was disappointing to be confronted by those conditions, but we produced a stunning performance in the field to come out of a game we were behind in on level terms.

"Spin won the day, but if you can't turn a ball on that wicket there isn't much hope for you. It was a loose and dusty surface, which you would expect bowlers of international calibre to perform on as well as they did.

"It is not for me to say whether Somerset should be docked points. There is a due process that will be followed by the cricket liaison officer and it is up to him how he views the pitch.

"If he rates it below average it will be the second one at Taunton to receive that rating in the last 12 months and in that event there is another process to follow."

Somerset director of cricket Andy Hurry:

"Paul Allott is entitled to his view about the pitch, as are 5,000 people who have watched a really entertaining game of cricket over two days. We didn't ask our groundsman to prepare a turning wicket and the fact is that batsmen on both sides failed to come up with a method to play on that surface.

"I have not spoken to the cricket liaison officer, but we will be informed of his report in the next few days. I have not seen evidence of excessive spin throughout the game, which there would need to be for the pitch to be deemed below average.

"Whatever happens, the result is a huge blow to our hopes of winning the title. There is so much riding on every game and that's what makes today so disappointing."

Title race scenario

• Following the tie against Lancashire, second-placed Somerset can only collect a maximum of 247 points this season.
• Surrey, therefore, need 52 points to win the title, not including any earned in their current game against Essex.
• If Surrey beat Essex, they will collect 22 points, and so will need another 30 to become champions.