There has been more embarrassment for Mark Sanford, the Republican governor of South Carolina, whose affair with an Argentine journalist has derailed his presidential ambitions and threatens to ruin his political career.

Sanford’s wife, Jenny, revealed that she had learnt of the affair earlier this year when she discovered a letter the governor had written to his lover, since identified as Maria Belen Chapur, a former television producer now living in Buenos Aires.

Sanford said she had told her husband to end the affair but he asked permission to travel to Argentina to talk to the woman face-to-face. “I said absolutely not,” his wife said. “It’s one thing to forgive adultery. It’s another to condone it.”

The governor’s wife said that when her husband announced he needed time alone this month, she warned him not to attempt to see his mistress.

She was stunned to learn that he had gone to Buenos Aires without telling his staff, and even more appalled when a local newspaper published extracts from e-mails that Sanford had sent to his lover.

“Despite the best efforts of my head, my heart cries out for you, your voice, your body, the touch of your lips, the touch of your fingertips and an even deeper connection to your soul,” he wrote, prompting one talk show host to label him “the wild bull of the pampas”.

A former investment banker from a wealthy Chicago family, Jenny Sanford has said she is prepared to consider reconciliation but on Friday she made no attempt to conceal her contempt for his behaviour.

Asked by one reporter about the governor’s political prospects, she snapped: “His career is not a concern of mine . . . I’m worried about my family and the character of my children.”

Formerly regarded as a leading Republican contender for the White House, Sanford is resisting calls for his resignation as governor. On Friday he issued a new apology to members of his state cabinet but told reporters that his inclination was to “carry on” in office.

Several state officials noted that barring further revelations about the use of state funds to finance Sanford’s romantic activities, South Carolina voters were likely to take their cue from Jenny Sanford. “If she forgives him, they might too,” one insider said.

Others argued that Sanford’s credibility had been fatally damaged. It was reported yesterday that a jealous Argentine boyfriend of Chapur found the e-mails on her computer and forwarded them to a South Carolina newspaper.

Sanford has also given birth to a new euphemism for adultery — “hiking the Appalachian trail” — the governor’s original explanation for his absence.

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