The Japanese prime minister has declined to say if he had nominated Donald Trump for the Nobel peace prize, though he emphasised he did not deny doing so.

Trump’s assertion on Friday that Shinzō Abe had nominated him for the honour and sent him a copy of the letter has raised criticism in Japan.

Questioned in parliament about Trump’s claim that he had done so, Abe said: “In light of the Nobel committee’s policy of not disclosing recommenders and nominees for 50 years, I decline to comment.”

Neither the prime minister nor his spokesman denied Trump’s comment.

“I never said I didn’t” nominate him, Abe said in response to a follow-up question by Yuichiro Tamaki, a lawmaker for the opposition Democratic Party for the People.

Tamaki tweeted on Monday that given the lack of progress on various issues with North Korea he was concerned such a nomination would “send the wrong message to North Korea and the rest of international society”.

In responding to Tamaki’s questions in parliament, Abe praised Trump, saying he “has been decisively responding toward resolving North Korea’s nuclear and missile problems, and last year he held historic US-North Korea summit talks”.

Abe added that Trump had also passed on to the North Korean leader, Kim Jong-un, Japan’s concerns about past abductions of Japanese citizens by North Korea, saying “he and the entire White House also actively cooperated in resolving the issue. I highly praise President Trump’s leadership,” Abe said.

Trump’s claim that Abe had sent him a “beautiful copy” of a letter sent to the Nobel committee could not be immediately verified.

The government’s top spokesman, Yoshihide Suga, echoed Abe’s remarks in refusing further comment.

The situation is awkward for Abe at a time when his government is under fire for allegedly manipulating data on wage increases to suggest his economic policies were yielding better results than was actually the case.

“Being Trump’s closest friend among world leaders has not worked out too well for Abe,” said Jeff Kingston, the director of Asian Studies at Temple University Japan. “He’s not making Abe look very good.”

Citing unidentified government sources, the Japanese newspaper Asahi Shimbun reported on Sunday that Abe had nominated Trump at the US president’s behest.

Barack Obama was awarded the Nobel peace prize in 2009, his first year in office, for laying out a US commitment to “seek the peace and security of a world without nuclear weapons”.

Trump complained on Friday that his predecessor was there “for about 15 seconds” before he was awarded the prize.

The deadline each year for nominations is midnight on 31 January. According to the Nobel committee website, there are 304 candidates for the 2019 peace prize. It says 219 are individuals and 85 are organisations.

Trump’s historic summit with Kim in Singapore last June was replete with pomp but thin on substance. The president’s comments on Friday drew speculation that the South Korean leader, Moon Jae-in, may have nominated Trump.

Kim Eui-kyeom, Moon’s spokesman, said he had not, and that he was unlikely to do so.

But Kim said Moon believed Trump “has sufficient qualifications to win the Nobel peace prize” for his work toward peace between North and South Korea, which have yet to sign a peace treaty after their 1950-53 war.

The US is Japan’s ally and anchor for national defence and Abe has assiduously cultivated cordial ties with Trump. He was the first foreign leader to meet Trump after he won the 2016 presidential election.

North Korea has refrained from nuclear and missile tests since early last year. The move was a welcome development for Japan, which is within the range of its missiles and has sometimes had test rockets land in its territorial waters.

Abe has a large political stake in making progress in resolving the abduction issue with North Korea, an important one for his nationalist political base.

The Nobel committee chooses the recipient of the prize in early October by a majority vote. The prize is awarded on 10 December in Oslo, Norway.