Longtime E! channel host Catt Sadler says she is leaving the company due to a "massive" pay disparity.

In a remarkable blog post on Tuesday evening, Sadler said she wanted to stay at E!, but the channel refused to pay.

She wrote, "How can we make it better for the next generation of girls if we do not stand for what is fair and just today?"

E!, an entertainment cable channel owned by NBCUniversal, disputed Sadler's suggestion that the gender pay gap was an issue in this case.

"E! compensates employees fairly and appropriately based on their roles, regardless of gender," a spokesperson told CNNMoney. "We appreciate Catt Sadler's many contributions at E! News and wish her all the best following her decision to leave the network."

Sadler, a host on E! since 2005, is one of the channel's best-known personalities.

Earlier this year she moved on from hosting "E! News" to a new daytime show called "Daily Pop," though she continued to appear on the channel's flagship news program.

Sadler's decision to leave leaked out on Monday, and Tuesday was her final day on the air.

After a farewell broadcast, she published her blog post, describing "a massive disparity in pay between my similarly situated male co-host and myself."

While Sadler didn't name him, Jason Kennedy was her co-host on "E! News" for years.

Related: Where the gender pay gap is the widest

Sadler said she found out about the wage gap earlier this year. "He wasn't just making a little more than I was. In fact, he was making close to double my salary for the past several years," she wrote.

She said E! wanted to renew her contract, so "my team and I asked for what I know I deserve and were denied repeatedly."

She described her thought process this way: "How can I operate with integrity and stay on at E if they're not willing to pay me the same as him? Or at least come close? How can I accept an offer that shows they do not value my contributions and paralleled dedication all these years?"

Related: The gender pay gap doesn't close - even at the very, very top

Sadler doesn't appear to have a next job lined up. She said "the unknown" is scary, as a single mother of two boys, but that she'll find more work and "be an agent for change."

Pay disparities in broadcasting have also come up in the past.

Mika Brzezinski, the co-host of "Morning Joe" on MSNBC, spoke out in 2011 about how she found out that Joe Scarborough made 14 times more money than she did.

Through multiple negotiations, Brzezinski narrowed the gap significantly. She wrote about the issue in a book called "Know Your Value." Sadler used a similar phrase in her blog post on Tuesday night: "Know your worth."