* Centre-right minister quits, denying corruption allegations
* Accuses Letta government of abandoning her
* Resignation adds to tension for ruling coalition over election reform (Adds quotes, political details, background)
By James Mackenzie
ROME, Jan 26 (Reuters) - Italian Agriculture Minister Nunzia De Girolamo resigned on Sunday, following heavy criticism after she was caught on tape discussing public contracts, adding a further complication to Prime Minister Enrico Letta's fragile coalition.
De Girolamo, a member of the small New Centre Right (NCD) party which supports Prime Minister Enrico Letta's left-right coalition, denied any wrongdoing in the affair and said that she had quit her ministerial post to defend her dignity.
"I cannot remain in a government which has not defended my honour," she said in a statement.
The resignation adds another twist to the delicate situation facing the coalition between Letta's centre-left Democratic Party (PD) and the NCD, already tested by strains over plans to reform electoral laws which could penalise smaller parties in a future election.
The PD said it took note of De Girolamo's resignation and her party colleague, Transport Minister Maurizio Lupi was quoted by RAI state television as saying he respected a decision of "great dignity".
De Girolamo faced pressure to resign after the emergence of a secret recording made in 2012, before she became a minister, in which she was heard apparently discussing the award of a contract to manage a hospital cafe in her home region of Benevento in southern Italy.
She always denied any wrongdoing, saying she had been framed, but she received notably little support from coalition partners or Letta himself when she defended herself in a half-deserted parliament earlier this month.
She was not under formal investigation but the opposition 5-Star Movement called a no confidence motion against her which had been due to be held on Feb. 4.
Italian newspapers said that she was likely now to rejoin Silvio Berlusconi's Forza Italia party which she left last year as part of a breakaway centre-right group that remained with Letta when Berlusconi quit the ruling coalition.
DELICATE TIME FOR GOV'T
The moment comes at a delicate time for the government as parliament prepares to debate new electoral reform proposals designed to replace the system blamed for the messy deadlock left by last year's election.
Letta, who visits Brussels this week keen to dispel any worries over political tensions, has faced pressure to reshuffle his cabinet but it was not immediately clear whether De Girolamo's departure would herald wider changes in the executive.
The chronically divided PD has itself been in a febrile mood ever since Matteo Renzi, an ambitious 39-year-old moderniser with little time for the traditions of the left, won a sweeping victory in a leadership primary last month.
Renzi, who is not in the government but who makes no secret of his desire to become prime minister in the future, has pressed for swifter action on economic and institutional reform, saying it would be better to go to early elections than delay further.
Angelino Alfano, head of the NCD and Letta's deputy prime minister warned earlier on Sunday that the tensions within the PD were putting the stability of the government at risk.
"If the Democratic Party doesn't support its own prime minister, this government cannot continue," Alfano told reporters on Sunday. (Reporting by James Mackenzie; Editing by Robin Pomeroy, Bernard Orr)