Labour's Barry Sheerman said the change "shrinks childhood" by making people adults at 16.
He spoke as MPs debated extending the franchise during the EU referendum, a move they then rejected in a vote.
Shadow Europe minister Pat McFadden said he respected Mr Sheerman but could see no link between extending voting rights and sexual abuse.
Huddersfield MP Mr Sheerman said: "Up and down this country we've had vulnerability to sexual predators and ghastly things happening right through to 18 and this move to have adults at 16 will make a lot of young men and women more vulnerable to sexual predation than that happens at the moment."
After Mr McFadden rejected this argument, Mr Sheerman added "what those of us - the small minority of us on these benches I have to say - worry about is" that if people are treated as an adult at 16 "that shrinks childhood".
Labour and the SNP support allowing 16 and 17-year-olds to vote in UK elections, but the government is against the policy.
Setting out his party's position, Mr McFadden said that aside from the wider debate about the voting age, there was a "very strong reason" to lower it for the EU referendum because young people's future was "directly at stake".
If the UK votes to leave the EU, their ability to live and study in Europe would be affected, he said.
But Conservative Cabinet Office Minister John Penrose said this was not the time to consider such a change, saying the issue should be "soberly and properly debated" on another occasion.
The change was rejected in a Commons vote by 310 to 265.
The bill, which will put into law the in/out referendum promised by 2017, is currently making its way through Parliament.
Also during the committee stage debate, an SNP motion to allow EU nationals resident in the UK to vote in the referendum was rejected by 514 votes to 71.

Takata has been hit by a huge recall of faulty and potentially deadly airbags used worldwide by carmakers.
It has been linked to 11 deaths and more than 100 injuries.
The shares dropped following a report from Bloomberg citing unnamed bidders.
Reports emerged last week that Takata was looking for private equity groups and other car part makers as investors to help it with its financial situation.
However, on Tuesday, Bloomberg reported that several bidders were considering a push for bankruptcy protection instead as it might mean lower repayments to debt holders.
The move would mean the company being put under administration so it can be restructured with the help of new investors.
Through this process, future investors can be relieved of some of the company's debts and obligations.
Takata has paid out $70m (£48m) in fines from US regulators so far over the faulty airbags.
In May, the company reported a net loss of 13.1bn yen ($128.7m, £99m) for its financial year ending in March.

The 30-year-old Scot, who raced for Force India from 2010 to 2013, will be back-up for race drivers Felipe Massa and Lance Stroll.
Deputy team principal Claire Williams said: "It's great for us to retain someone of Paul's experience."
Di Resta will combine F1 duties with racing for Mercedes in Germany's DTM touring car series.
He said he was "delighted" to stay at Williams and "looking forward to understanding the new regulations" introduced to F1 this season in an attempt to make the cars faster, more dramatic and more appealing to the audience.
Williams' new car will be revealed to the public on Friday before pre-season testing starts in Spain on 27 February.
Di Resta's best race results in F1 have been two fourth places in Singapore in 2012 and Bahrain in 2013. He was the DTM champion for Mercedes in 2010.
Part of his responsibilities at Williams will involve helping Brazilian veteran Massa, 35, support Stroll, an 18-year-old Canadian rookie who brings financial backing reported to be at least £20m to the team.
Massa retired at the end of last season but was persuaded to come back for one final year after Mercedes approached Williams to release Valtteri Bottas to them following world champion Nico Rosberg's retirement.
Allowing 16-year-olds to vote will make them more vulnerable to sexual abuse, an MP has said.
[NEXT_CONCEPT]
Takata shares have fallen almost 12% after a report that potential bidders are considering bankruptcy proceedings for the company to mitigate their liability following the firm's airbag scandal.
[NEXT_CONCEPT]
Paul di Resta is to stay as Williams reserve driver for a second season in 2017.