Embattled Labor frontbencher Sam Dastyari has refused to step aside over "cash for comment" allegations, insisting the opposition leader has not requested his resignation.  But while admitting he made a mistake asking a Chinese company linked to Beijing to pay off a personal travel debt, Senator Dastyari denies it influenced his stance on the dispute in the South China Sea.  Labor leader Bill Shorten is standing by Senator Dastyari despite mounting pressure for his head over the $1600 payment and reports he said Australia should remain neutral and respect China in the territory dispute.  The shadow minister, and manager of Labor's business in the Senate, won't admit he presented a contrary view to government and Labor policy at a media conference.  "I support the Labor Party position on the issue of the South China Sea," he declared at his first press conference on the matter in Sydney on Tuesday.  "If there is an instance in which I have misspoken or been misquoted, then that is wrong."  Mr Shorten has "very strongly" counselled the Labor senator, who played down his request for payment as a rushed decision made without consideration.  Pressed on why he chose the company Top Education to foot the bill, the senator said it was "a firm that I knew in Sydney".  "It would have been inappropriate, regardless of who I had asked."  Despite increasing pressure to resign, Senator Dastyari, who was recently promoted to the outer shadow ministry, is standing firm.  "I haven't offered and I haven't been asked," he said.  Earlier, the opposition leader backed his 33-year-old NSW senator, declaring he deserved a second chance because he was a "bright young man".  Senator Dastyari's senior roles didn't stop Mr Shorten playing down his rank on Tuesday, repeatedly referring to him as a "junior senator".  "I've spoken to him severely and I've made it crystal clear that this behaviour is not the behaviour I expect in the future from him," Mr Shorten told reporters in Melbourne on Tuesday.  "I am prepared, however, to give him a second chance."  The saga has reignited the debate about banning foreign donations, with conservative senators Cory Bernardi and Eric Abetz joining Labor calls for reform.  Prime Minister Malcolm Turnbull hasn't ruled out backing donation changes, saying the issue would be considered by a parliamentary committee on electoral matters in the usual way.  The prime minister accused Senator Dastyari of taking cash for himself and then expressing a view at odds with his party's foreign policy.  "What Mr Shorten is seeking to do is distract attention from the very real failure of his leadership in not removing Sam Dastyari from the front bench," he told reporters in Hangzhou on Tuesday.  Shadow attorney-general Mark Dreyfus earlier rejected calls for Senator Dastyari to stand aside, insisting his colleague had made full disclosure, broken no law and had donated the amount to charity.  He said foreign donations could be banned next week if the Liberal Party supported it.  The coalition should instead look at its own books, he said, such as Chinese donations Foreign Minister Julie Bishop secured for the West Australian branch of the Liberal Party.  Greens leader Richard Di Natale says ministers have been sacked for a lot less, but stopped short of calling for Senator Dastyari's head.
Liberal backbencher Cory Bernardi says only voters on the electoral roll should be allowed to make political donations.