On one tape, recorded three days before Sergeant Steven Roberts, from Bradford in North England, was shot in the chest and killed, he said troops were not getting the equipment they had been promised.
"It's disheartening because we know we are going to war without the correct equipment," he said.
The revelation of the tapes on Thursday has reignited criticism in Britain about the supplies and equipment provided to troops sent to Iraq.
Government reports have acknowledged that body armour, uniforms, and chemical suits all failed to reach some troops in the front line and that tanks never received filters to protect against nuclear, chemical and biological contamination.
The opposition Conservative Party has called for the resignation of Defence Minister Geoff Hoon over Roberts' death.
Roberts, 33, who served with the 2nd Royal Tank Regiment, was shot in the chest and killed in action near al-Zubayr, southwest of Basra, in March 2003.
A pathologist's report found that the bullet would have been stopped by a specialist body vest, which had ceramic plates to cover the heart and aorta.
Roberts had been ordered to give up the vest to a soldier deemed more at risk, and Roberts was left with standard armour.
A wife's anger
On another tape released by his wife, Samantha, he said: "We are now back into one of the camps to up-armour, which again is a bit of a joke in itself because they are running out of the frontal armour.
British troops may stay on in Iraq
"It will be interesting to see what armour I actually get. I will keep you posted," he added.
Samantha Roberts said she was given the tapes by a colleague of her husband on the day of his funeral.
She said she felt compelled to release the tapes, which also contain personal sentiments, because she was angry that Hoon refused to accept responsibility on behalf of the government for her husband's death.
"It's obviously something that's very close to my heart but when you're banging your head against a brick wall, you feel you've got no option but to let people see it," she said.
Prime Minister Tony Blair expressed his sympathy and condolences for Mrs Roberts and said he "totally" understood her concerns.
Blair declined to comment further on the tapes or the allegations of equipment problems ahead of the findings of a Ministry of Defence investigation into Roberts' death.
Nicholas Soames, defence spokesman for the opposition Conservative Party, said that the taped diaries confirm that the government was negligent.
Samantha Roberts backed calls by Soames for Hoon to resign.
"It's for the benefit of the country for him to go."