White House advisor Kellyanne Conway listens as US President Donald Trump meets with county sheriffs at the White House in Washington, US February 7, 2017. [Photo/Agencies]

WASHINGTON - Senior White House adviser Kellyanne Conway drew sharp criticism from a top Republican lawmaker and complaints on Thursday over the ethics of using her position to promote product lines of President Donald Trump's daughter Ivanka, a day after he attacked a retailer for dropping them.

Federal ethics rules prohibit executive branch employees from using their positions to endorse products or for the private gain of friends. The law does not apply to the president.

"Go buy Ivanka's stuff ... I'm going to go get some myself today," Conway told Fox News in an interview from the White House. "I'm going to give a free commercial here: Go buy it today, everybody."

On Wednesday, President Trump attacked department store chain Nordstrom Inc for dropping his daughter's products, drawing intense criticism for using a White House twitter platform to intervene in a commercial matter involving his family's business ties.

Nordstrom said it dropped the brand for its poor performance.

Online sales of Ivanka Trump branded products fell 26 percent in January 2017 compared to the same period a year earlier, according to retail analytics firm Slice Intelligence which shared its findings with Reuters. The company analyzed data from e-mail receipts of over 4 million US online shoppers.

The data also showed sales of the Ivanka Trump brand declined in the second half of 2016 at all online retailers including Amazon.com Inc, which sells most of the brand's merchandise. In-store sales of the Ivanka Trump brand was not available.

Republican Jason Chaffetz, chairman of the House of Representatives Oversight committee, told The Associated Press Conway's promotion of the brand was "clearly over the line, unacceptable."

Chaffetz spokeswoman M.J. Henshaw confirmed his comments.