Labour’s Kerry McCarthy is to submit letters to the party which she says show she received “unwanted attention” from a fellow MP, the BBC understands.
The member for Bristol East claims she was sent “upsetting” correspondence from Kelvin Hopkins, the MP for Luton North, over a period of about 20 years.
Mr Hopkins 76, said the complaint had caused him “unbearable” stress.
He is currently suspended from the party in connection with a separate allegation, which he denies.
Ms McCarthy, 52, a former shadow environment secretary, will hand the file to Labour party officials on Monday, the BBC has learned.
She alleges Mr Hopkins sent her a series of letters and cards commenting on her appearance, including one in which he described having a dream about her.
The former Labour frontbencher said she believed Mr Hopkins, who urged her in two of the notes to “dispose” of them, knew his actions were wrong.
“I never responded in any way, I never gave him any encouragement in any way, I tried to keep my distance as much as possible,” she said.
“I absolutely believe he knew this behaviour was unacceptable. It made me feel uncomfortable in his presence and was quite upsetting.”
In a statement, Mr Hopkins said her complaint had caused him “immense personal hurt and utter dismay” from someone he regarded as a friend.
“I cannot understand why a parliamentarian of such experience and standing, who is also such a long-term friend, would not have told me that she was unhappy with any aspect of our friendship rather than going straight to the national press,” he said.
“At a minimum I would have expected a parliamentary colleague to raise any complaint through normal channels, allowing me due process and a fair chance to defend myself, if necessary.
“I do ask, on my behalf and on behalf of all other individuals and their families dealing with allegations, that these matters are dealt with by proper due process and not by unfair, humiliating one-sided trial by media.
“I am a 76-year old man and the stress this has caused me and my family is unbearable.”
The MPs first met when Ms McCarthy was in her late 20s and they were both involved in Labour politics in Luton.
After a lunch in 1994, the purpose of which she believed was to discuss politics she said, he sent her a card saying he had invited her “because you are attractive, intelligent and charming”.
More notes and cards followed over the next three years, she claimed, but they then stopped until her 50th birthday.
A final letter, sent some time in 2015/16, said Mr Hopkins had a dream about Ms McCarthy and she remained a “very attractive woman”.
She said she decided to go public after the “bravery” of a young activist, Ava Etemadzadeh, who complained last week about the behaviour of Mr Hopkins.