Peterborough took a giant stride towards automatic promotion with a 3-1 derby triumph that plunged fierce rivals Northampton deeper into relegation trouble.

Sammie Szmodics hit a brace before leading scorer Jonson Clarke-Harris helped himself to his 30th goal of the campaign as Posh moved level with League One leaders Hull.

Szmodics provided a 33rd-minute breakthrough when he darted into the box to fire home a low Dan Butler cross from the left, but skipper Mark Beevers then handed Cobblers a lifeline.

Beevers clumsily impeded Town frontman Alex Jones as he attempted to cut out a Nathan Thompson back-pass and Sam Hoskins struck from the penalty spot in the 43rd minute to level.

Posh regained the initiative as Szmodics provided a perfect start to the second half, lifting the ball over advancing Cobblers keeper Jon Mitchell and finishing into the empty net in the 48th minute after being picked out by Jack Taylor.

And the points were sealed when Clarke-Harris slammed a 67th-minute penalty past Mitchell after Nathan Thompson was dumped to the deck by Hoskins with Northampton remaining in the bottom four.